Adhesive

ABSTRACT

Disclosed is an adhesive that may include two or more starches or starch derivatives with different molecular weights. In many embodiments, the adhesive includes (1) unmodified or slightly thinned starch, (2) maltodextrin or syrup solid, and (3) a hydroxypropyl starch. In most embodiments, the adhesive includes a plasticizer. The adhesive may be prepared by blending the starch and starch derivatives, and cooking the blended slurry, preferably under acidic conditions. The adhesive may be employed for various purposes including as an adhesive for a multi-wall bag.

RELATED APPLICATION

This application claims benefit of U.S. Provisional Application No.61/333,017, filed May 10, 2010, which is incorporated herein byreference in its entirety.

TECHNICAL FIELD

In general, some embodiments of the invention are in the field ofadhesives and related methods, including methods of preparing anadhesive and methods of using an adhesive. Certain embodiments of theinvention are in the field of starch derivatives, including adhesivesprepared from starch derivatives. In some embodiments, the inventionprovides a lamination adhesive for packaging products such as multi-wallbags.

BACKGROUND

Starch and starch-derived dextrins commonly have been used for manyyears as components in adhesives. Typical applications of starch anddextrin adhesives include corrugated box board, envelopes, bottlelabeling, paper bag seams, stamps, wallpaper, and laminates. Starch anddextrins have many advantageous attributes for use as adhesives, such astheir typical low cost, the abundance of starch, insolubility of starchand dextrins in fats and oils, and lack of toxicity.

In adhesive applications, starches and dextrins provide a good adhesivebase, but by themselves are not often used as adhesives in certainapplications. For many industrial uses, starches and dextrins arecombined with other additives such as polyvinyl acetate, or polyvinylalcohol. These additives are not only often times derived from petroleumsources, but can significantly raise the cost associated with producingthe adhesive.

In particular, in lamination adhesives for multi-wall bags, it isdesirable to have an adhesive that adheres well to polyethylene and topaper. There is a large market for multi-wall bags. Many such bags areshipped as a multi-wall laminar structure, the structure including paperand polyethylene, for instance, and sometimes including multiple layers.The individual layers within the multi-wall bag typically are adheredtogether with adhesive. In such applications, it is desirable for theadhesive to be sufficiently strong to achieve a cohesive bag that willbe able to retain the intended contents and that will not delaminateupon filling, handling, and transport. In many embodiments, it isdesirable that the adhesive have a “fiber tear” property, such that theadhesive is sufficiently strong to tear a paper or polyethylenesubstrate upon application of a tearing force.

In light of the wide levels of availability of starch products,starch-based lamination adhesives have been attempted. As starch ismodified (typically with acid) to reduce the molecular weight, thesolids level of a liquid starch adhesive can be increased. Starch basedadhesives have been made in the 30% solids range using this method.Variations incorporate other modifications, including the use ofpropylated, ethylated, and oxidized starches. These adhesives work wellfor paper to paper applications, and they may also work in some limitedpaper to non-porous applications. However, they do not exhibit affinityto polyethylene or to other surfaces that are difficult to adhere. Inaddition, it is difficult to achieve a workable adhesive with a solidscontent greater than about 30%. Generally, higher solids contents aremore desirable in adhesives, because the liquid component of theadhesive can warp or otherwise damage certain substrates, and a highersolids content generally correlates to a shorter drying time.

Starch derivatives have been used as adhesives. For instance,maltodextrin and syrup solids have been employed. Maltodextrin has anaffinity for polyethylene. Additionally, maltodextrin has a lowmolecular weight relative to starch, thereby allowing for a relativelyhigh solids content (around 65%) in an adhesive. Upon drying, however,maltodextrin becomes brittle. Additionally, maltodextrin has lowcohesive strength relative to starch. Hydroxypropyl starch (such asP30L, a starch presently available from Grain Processing Corporation ofMuscatine, Iowa) is an adhesive that adheres well to polypropylene, but,for reasons not well understood, does not adhere well to polyethylene.

SUMMARY

It has now been found that an adhesive can be prepared using acombination of starch and a starch derivative, such as a maltodextrin.In most embodiments, three different starch-based products are employed,these including (1) unmodified or slightly thinned starch, (2)maltodextrin or syrup solid, and (3) a modified starch, such ashydroxypropyl starch, or waxy starch. In some embodiments, the adhesiveincludes a plasticizer. The modified starch should be a film-formingstarch that is resistant to retrogradation in the intended adhesiveapplication.

In some embodiments, the adhesive is prepared by blending the starch andstarch derivatives in a slurry, and cooking the slurry. Any suitablecooking apparatus may be employed, but a preferred apparatus is ajet-cooking apparatus. The slurry may be thinned with acid during orafter cooking.

Thus, in some embodiments, the invention provides an adhesive, theadhesive comprising an unmodified or slightly thinned starch, apartially hydrolyzed starch derivative, the starch derivative beingpresent in an amount effective to provide affinity to polyethylene, anda modified starch, the modified starch being present in an amounteffective to inhibit retrogradation of the starch component of theadhesive. In some embodiments, the invention provides a process thatcomprises providing a mixture comprising an unmodified or slightlythinned starch, a partially hydrolyzed starch derivative, and a modifiedstarch, and jet-cooking the mixture under conditions suitable to form anadhesive, the starch derivative being present in said mixture in anamount effective to provide affinity to polyethylene in said adhesive,the modified starch being present in said mixture in an amount effectiveto inhibit retrogradation of the starch component in said adhesive. Thestarting mixture may be jet-cooked under acidic conditions.

DETAILED DESCRIPTION

Generally, an adhesive may include two (or more) starches or starchderivatives with different molecular weights. In many embodiment, theadhesive includes (1) an unmodified or slightly thinned starch, (2) apartially hydrolyzed starch derivative, such as a maltodextrin or syrupsolid, and (3) a hydroxypropyl or other modified starch or a waxystarch. In most embodiments, the adhesive includes a plasticizer. Thestarch and starch derivatives may be obtained from any suitable grain,such as corn, wheat, rice, potato, or the like. Preferred ranges for thevarious ingredients are set forth below

-   -   Maltodextrin or syrup solid: 25-75%    -   Modified Starch: 1-15%    -   Unmodified Starch: 1-15%    -   Plasticizer: 1-30%    -   Water: 30-75%

Although it is not intended to limit the invention to a particulartheory of operation, it is believed that each component of the adhesiveperforms certain functions or otherwise provides benefits. Theunmodified starch is believed to impart cohesive strength, and also isless expensive in many cases than the modified starch. Any suitableunmodified starch may be employed. Corn starch is preferred, but anyother suitable starch may be employed. The starch may be unmodified assupplied, or may be slightly acid thinned.

When a maltodextrin is employed, it may have any suitable dextroseequivalent value. Suitable maltodextrins are sold by Grain ProcessingCorporation under the product names MALTRIN@, M040, M050 M100, M150, andM180. Other starch derivatives, such as syrup solids or polydextroses,may be employed The maltodextrin or starch derivative is believed toprovide an affinity for polyethylene, and also to enable the adhesive tohave a higher solids content. Hydrogenated maltodextrins and otherstarch derivatives may be employed.

The propylated starch, or other suitable modified starch, is believed toprovide cohesion and to assist in limiting retrogradation of the starchcomponent of the adhesive. The modified starch may be derivatized to anysuitable degree of substitution. The starch may be derivatized with anysuitable material. Alternatively, or in addition thereto, a waxy, highmolecular weight starch may be employed.

The plasticizer is believed to impart flexibility. Any suitableplasticizer, such as glycerin, may be employed. Other suitableplasticizers include polyalkylene alcohols. In some embodiments, theplasticizer may be present in an amount ranging from about 5-30%.

These ingredients may be present in amounts effective for theirrespective purposes. The adhesive may include other materials, such asbiocides, colorants, and so forth. If other ingredients are present,they may be present in any amounts suitable for their intended purpose.

The adhesive may be prepared by any suitable method, such as batchcooking or jet cooking the ingredients. The preferred method is viaforming a slurry and jet-cooking the slurry. In many embodiments, acidis added to the slurry before cooking to bring the pH in the range from2.8 to 4.0. Any suitable jet-cooking apparatus and conditions may beemployed. Exemplary conditions are provided hereinbelow in the Examples.

An adhesive prepared in accordance with the preferred teachings hereinhas several desirable properties. The solids content can be made to bein excess of 25%, and in some embodiments in excess of 30%, and in someembodiments in excess of 35%, and in some embodiments in excess of 40%,and in some embodiments in excess of 45%, and in some embodiments inexcess of 50%, and in some embodiments in excess of 55%, and in someembodiments in excess of 60%, and in some embodiments in excess of 65%.A solids content of 50-55% is preferred. The adhesive can have goodaffinity and adhesion to both polyethylene and polypropylene, as well aspaper. The adhesive can be made to be flexible to facilitate handling.Also, the adhesive may be formulated to have some tack, such that ifthere is a momentary separation between the materials to be adheredtogether, the adhesive will not fail. The adhesive can be made to adherewell to glass as well as metallic material.

The following examples and comparative examples are provided forillustration.

Comparative Example 1 Ethylated Starch Adhesives

The following adhesive formulations were prepared with ethylated starch(GPC K96F). Each formulation was prepared with the below indicatedcomponents along with water to bring the total sample size to 800 g.

Ethylated Ethylated Starch in Starch in grams grams PVOH* (44% solids(43% solids BAN (C203SF Na Sample slurry) slurry) enzyme* PVOH) PVP*borate* HCl* C1A 352 0.0426 C1B 344 0.08 5 4 1 C1C 352 2.84 *% on a drystarch solids basis C1A: Indicated amounts of ethylated starch and waterwere slurried in an atmospheric cook container. BAN enzyme (amylaseenzyme), slurried with a minimum amount of water, was added. The slurrywas cooked at 195° F. for 20 minutes and reactions were terminated withaddition of 2 ml of hydrogen peroxide. C1B: Indicated amounts ofethylated starch, polyvinyl alcohol (PVOH), polyvinyl pyrrolidone (PVP),sodium borate and water were slurried in an atmospheric cook container.BAN enzyme, slurried with a minimum amount of water, was added. Theslurry was cooked at 180° F. for 60 minutes and reactions wereterminated with addition of 2 ml of hydrogen peroxide. C1C: Indicatedamounts of ethylated starch, HCl and water were slurried in anatmospheric cook container along with antifoam (0.85% on a dry starchsolids basis).

The slurry was cooked at 200° F. for 20 minutes and reactions wereterminated with addition of sodium carbonate (1.56% on a dry starchsolids basis).

Bonding Strength

Spot adhesion tests were used to determine effectiveness of the adhesivefor paper/paper adhesion and polyethylene (PE)/paper adhesion. The testwas conducted by placing one drop of glue on a 3×5 inch plastic cardover a 0.5 inch diameter hole in the card and scraping away the excess.About 0.10 gram of adhesive was transferred to a paper underneath thecard. Either polyethylene or a second sheet of paper was placed on theglue spot and an 8×8 inch steel weight of 593 grams was placed on theglue spot for 30 seconds. Samples were pulled apart after a period oftime, generally 24 hours, and evaluated qualitatively. Materials thatexhibited “good” or “excellent” results showed fiber tear properties,and were deemed suitable for commercial use.

Sample Description Paper/Paper PE/Paper C1A Ethylated starch poor poorC1B Ethylated starch/PVOH/PVP fair fair C1C Ethylated starch/acid fairpoor

Comparative Example 2 Ethylated and Propylated Starch Slurries andAdhesives

An ethylated starch slurry (slurry 2-1) was prepared by blending GPCK98F with water to provide a 42% solids slurry. The pH was adjusted to2.5 with 6N H₂SO₄. The slurry was jet cooked at 300° F. through a 5minute loop.

A propylated starch slurry (slurry 2-2) was prepared by blending GPCB790 with water to provide a 40% solids slurry. The pH was adjusted to2.51 with 6N H₂SO₄. The slurry was jet cooked at 300° F. through a 5minute loop.

The following blends were prepared and tested according to the proceduredescribed in Example 1.

Sample Description Paper/Paper PE/Paper C2A 33% slurry 2-1good/excellent fair 33% slurry 2-2 33% latex 1% borate C2B 25% slurry2-1 excellent poor 25% slurry 2-2 25% latex 25% Sample 4A (Ex. 4) C2C30% slurry 2-1 good poor 30% slurry 2-2 40% latex C2D 20% slurry 2-1good/excellent poor 20% slurry 2-2 40% latex 20% Sample 4A (Ex. 4)

Example 1 Propylated Starch Adhesives

A maltodextrin slurry was prepared by blending GPC MALTRIN M180 withwater to form a slurry containing 68% solids. Acid modified starch wasprepared by blending GPC T300 with water to form a slurry containing 12%solids. A propylated starch, GPC P30L, was supplied. A sample ofcombined cooked ingredients was prepared by adding the above-identifiedcomponents in the following amounts:

Amount (g) P30L 45% 360 M180 (35% slurry) 280 T300 (20% slurry) 160

This sample had good/excellent paper to paper adhesion and fair/goodPE/paper adhesion.

Comparative Example 3 Ethylated Starch/Cationic Starch Blends

The following adhesive formulations where prepared with ethylated starch(GPC K96F). Each formulation was prepared with the below indicatedcomponents along with water to bring the total sample size to 800 g.

Ethylated Ethylated Starch in Starch in PVOH* grams grams (C203 (44%solids (42% solids BAN SF Na Sample slurry) slurry) enzyme* PVOH) PVP*borate C3A 352 0.0492 C3B 336 0.08  5 4 1

C3A:

The indicated amounts of ethylated starch and water were slurried in anatmospheric cook container. BAN enzyme slurried with a minimum amount ofwater was added. The slurry was cooked at 195° F. for 20 minutes andreactions were terminated with addition of 2 ml of hydrogen peroxide.The cooked ethylated starch slurry (250 g) was blended with 250 grams ofcationic starch paste (GPC L340).

C3B:

The indicated amounts of ethylated starch and water were slurried in anatmospheric cook container. BAN enzyme slurried with a minimum amount ofwater was added. The slurry was cooked at 195° F. for 30 minutes andreactions were terminated with addition of 2 ml of hydrogen peroxide.The cooked ethylated starch slurry (312 g) was blended with 102 grams ofcationic starch paste (GPC L340).

Bonding strength was tested as described in Example 1 and was asfollows.

Sample Description Paper/Paper PE/Paper Comments C3A Ethylated/cationicstarch Good poor unstable C3B Ethylated/cationic good fair unstablestarch/PVOH/PVP/acid

Comparative Example 4 Ethylated Starch/Latex Blends

Ethylated starch/latex blends were prepared as follows. Bonding strengthwas tested as described in Example 1. Dispersant (0.1% Dipex N-40, basedon starch slurry weight) was added to each sample and all components foreach sample were blended on a high shear mixer for 4 minutes at 22 rpm.

Formula 1879-9-2 Sample (grams) Latex* Paper/Paper PE/Paper C4A 320 1good poor C4B 315 2.5 good poor C4C 330 5 excellent poor *Latex was DOWCP620NA (carboxylated styrene-butadiene latex); amounts are % based onstarch slurry weight.

Comparative Example 5 and Example 1 A Starch Blends

The following starch blends were prepared. Bonding strength was testedas described in Example 1.

C5D and C5E:

Indicated amounts of propylated starch (GPC B790), maltodextrin (M180),waxy starch and water were slurried in an atmospheric cook container.The slurry was cooked at 212° F. for 30 minutes.

C5F:

Indicated amounts of propylated starch (GPC B790), maltodextrin (M180),waxy starch and water were slurried in an atmospheric cook container.The slurry was cooked at 212° F. for 30 minutes. The indicated amount ofglycerin was added after cooling at 5% on a collected weight basis.

C5G:

Indicated amounts of OS MALTRIN, unmodified starch (GPC B200),propylated starch (GPC B990), and water were slurried in an atmosphericcook container. The slurry was cooked at 212° F. for 30 minutes.

C5H:

The indicated amount of waxy starch was jet cooked at 300° F. through a5 minute loop. The sample was cooled to 140° F. and indicated amounts ofQuat and NaOH were added. The sample was stirred for 3 hours and the pHwas reduced to 4.0 with addition of HCl. Biocides were added at 0.15%based on the total weight of the sample.

C5I:

The indicated amount of waxy starch was jet cooked at 300° F. through a5 minute loop.

C5J:

Indicated amounts of maltodextrin (M180), OS MALTRIN, waxy starch,propylated starch (GPC B990), and water were slurried in an atmosphericcook container. The slurry was cooked at 212° F. for 30 minutes.

C5K:

The indicated amount of maltodextrin (M180) was slurried with warmwater. An equal amount of C5I was added to provide a 50/50 weightmixture.

C5L:

The indicated amounts of propylated starch and latex (Dow CP620NA) wereadded separately and stirred together.

1A:

Indicated amounts of maltodextrin (M180), propylated starch (GPC B790),waxy starch and water were slurried in an atmospheric cook container.The slurry was cooked at 212° F. for 30 minutes. The indicated amount ofglycerin was added after cooling at 5% on a total weight basis.

Sample Description Paper/Paper PE/Paper C5D 39.4% M180 Fair Fair 13.3%B790 1.42% Waxy 45.9% water C5E 26.3% M180 Good/ Fair 22.0% B790Excellent 1.2% Waxy 50.5% water C5F 25.0% M180 Excellent Fair 21.0% B7901.1% Waxy 4.8% glycerin 48.1% water C5G 39.3% OS Excellent Fair 2.3%B200 3.0% B990 55.4% water C5H 30.0% Waxy Good Poor 2.3% Quat 2.4% NaOH65.3% water C5I 31.5% Waxy Excellent Poor 68.5% water C5J 21% M180Excellent Poor 16.8% OS MALTRIN 2.7% Waxy 3.0% B990 56.5% water C5K31.5% M180 Good Poor 9.9% waxy 58.6% water C5L 50% P30L (30% solids)Good Poor 50% latex (@ 50% solids) 1A 37.5% M180 Good Good 11.2% B7901.9% Waxy 4.8% glycerin 44.6% water C5M cationic starch paste L340 GoodFair C5N cationic starch paste L360 Excellent Poor C5O cationic starchpaste L435 Good Poor

Comparative Example 5A Maltodextrin/Acid Modified Starch Blends

Maltodextrin/acid modified starch blends having the followingcompositions were prepared by dry-blending maltodextrin and starch andadding water.

C150 acid C165 acid C140 acid modified modified modified maltodextrinstarch starch starch slurry slurry slurry slurry Water Sample g (%) g(%) g (%) g (%) g (%) C5P 244.8 (30.6) 72 (9) 40 (5) 443.2 (55.4)

All ingredients for each sample were mixed together and cooked in anatmospheric cooker at 200° F. for 20 minutes. Bonding strength wastested as described in Example 1 and was as follows.

Sample Description Paper/Paper PE/Paper Comments C5PMaltodextrin/C165/C140 good Poor starch not cooked

“Starch not cooked” signified that the starch remained granular and themaltodextrin appeared to absorb water.

Comparative Example 6 Maltodextrin/Acid Modified Starch/PropylatedStarch Blends

The indicated amounts of maltodextrin (M180), propylated starch (B990),acid modified starch (C140), and water were mixed together and cooked inan atmospheric cooker at 212° F. for 30 minutes. Bonding strength wastested as described above and was as follows.

Sample Description Paper/Paper PE/Paper Comments C6A   34% M180 fairpoor starch not  4.5% B990 cooked  4.2% C140 57.3% water C6B 35.7% M180fair poor starch not  3.0% B990 cooked  4.5% C140 56.8% water

Example 2 and Comparative Example 6 B Maltodextrin/UnmodifiedStarch/Propylated Starch Blends

Maltodextrin/unmodified starch/propylated starch blends were prepared asfollows.

maltodextrin unmodified propylated slurry starch slurry starch slurrywater Sample g (%) g (%) g (%) g (%) 2A   294 (36.75)   18 (2.25) 24 (3)  464 (58) C6B 268.8 (33.6) 25.6 (3.2) 24 (3) 481.6 (60)

All ingredients for each sample were mixed together and cooked in anatmospheric cooker at 212° F. for 30 minutes with no acid modification.Bonding strength was tested as described in Example 1 and was asfollows.

Paper/ Sample Description Paper PE/Paper Comments 2A Maltodextrin/ Fairgood/ Consistency not unmodified starch/ excellent smooth propylatedstarch C6B Maltodextrin/ Fair Fair Gelled unmodified starch/ propylatedstarch 2B 2A + 7.5% glycerin excellent good/ Consistency not excellentsmooth 2C 2B + 5% glycerin good/ good/ Consistency not excellentexcellent smooth 2D 2C + 2.5% glycerin good/ good/ Consistency notexcellent excellent smooth

Comparative Example 7 Maltodextrin/Ethylated Starch andMaltodextrin/Ethylated Starch/Unmodified Starch Blends

Maltodextrin/unmodified starch/ethylated starch blends were prepared asfollows.

maltodextrin ethylated unmodified slurry starch slurry starch slurrywater Sample g (%) g (%) g (%) g (%) C7A 280 (35) 120 (15) 400 (50) C7B294 (36.75)  24 (3) 1  8 (2.25) 464 (58) C7C 168 (21) 126 (15.8) 22.4(2.8) 483.6 (60.4)

All ingredients for each sample were mixed together and cooked in anatmospheric cooker at 212° F. for 30 minutes. Bonding strength wastested as described in Example 1 and was as follows.

Sample Description Paper/Paper PE/Paper Comments C7AMaltodextrin/ethylated fair poor gelled starch C7BMaltodextrin/ethylated/ too thin too thin too thin unmodified starch C7CMaltodextrin/ethylated/ fair poor gelled unmodified starch

Example 3 and Comparative Example 8 Maltodextrin/PropylatedStarch/Unmodified Starch Blends and Maltodextrin/PropylatedStarch/Ethylated Starch Blends

Maltodextrin/unmodified starch/propylated starch blends andmaltodextrin/propylated starch/ethylated starch blends were prepared asfollows.

pro- eth- un- pylated ylated modified Maltodextrin starch starch starchslurry slurry slurry slurry water glycerin Sample g (%) g (%) g (%) g(%) g (%) % C8A 280 36   22.4 461.6 (35)   (4.5) (2.8) (57.7) 3A 294 2418 464   7   (34.1) (2.8) (2.1) (54)   3B 294 24 18 464   4.8 (35)  (2.9) (2.1) (55.2) 3C 294 24 18 464   2.4 (35.9) (2.9) (2.2) (56.6) C8B224 24 200 352   (28)   (3)   (25) (44)  

Glycerin was added after cooling of the sample. All ingredients for eachsample were mixed together and cooked in an atmospheric cooker at 212°F. for 30 minutes. Bonding strength was tested as described in Example 1and was as follows.

Paper/ Sample Description Paper PE/Paper Comments C8AMaltodextrin/propylated/ fair fair gelled unmodified starch 3AMaltodextrin/propylated/ excellent excellent Consistency unmodifiedstarch + not smooth glycerin 3B Maltodextrin/propylated/ good/ good/Consistency unmodified starch + excellent excellent not smooth glycerin3C Maltodextrin/propylated/ good/ good/ Consistency unmodified starch +excellent excellent not smooth glycerin C8B Maltodextrin/propylated/gelled gelled gelled ethylated starch

Example 4 and Comparative Example 9 Maltodextrin/PropylatedStarch/Unmodified Starch Blends Made with Jet Cooking

Maltodextrin/unmodified starch/propylated starch blends were prepared asfollows.

maltodextrin propylated unmodified pH after slurry starch slurry starchslurry water glycerin mixing Final Sample g (%) g (%) g (%) g (%) %ingredients pH 4A 4410 (34.3) 456 (3.5) 450 (3.5) 6684 6.6 (52) 4B 5040(42) 600 (5) 585 (4.9) 5775 4.0 (48.1) 4C 5355 (44.6) 648 (5.4) 630(5.3) 5367 3.82 (44.7) 4D 5670 (44) 684 (5.2) 675 (5.2) 4971 7 3.35 5.35(38.5) 4E 5670 (44) 684 (5.20 675 (5.3) 4971 7.5 3.15 6.7 (38.5) 4F 5985(46.4) 624 (4.8) 585 (4.5) 4806 7 3.15 6.7 (37.3)

Additional ingredients were added in some cases, as set forth in thetable below. Glycerin was added after cooling of sample. The pH wasadjusted to the indicated pH level after mixing ingredient togetherbefore jet-cooking. Final pH was adjusted as indicated after biocide wasadded using 50% NaOH.

All ingredients were mixed together and jet cooked at 300° F. through a5 minute loop. Bonding strength was tested as described in Example 1 andwas as follows.

Sample Description Paper/Paper PE/Paper Comments 4AMaltodextrin/propylated/ excellent excellent slow unmodified starch +dry time glycerin C9A 50% 4A excellent poor 50% latex 4BMaltodextrin/propylated/ good good gelled unmodified starch 4CMaltodextrin/propylated/ fair/good good gelled unmodified starch 4DMaltodextrin/propylated/ excellent fair/good gelled unmodified starch +glycerin C9B 75% 4D excellent fair 5% glycerin 20% waxy 4EMaltodextrin/propylated/ excellent fair/good gelled unmodified starch +glycerin 4E1 4E with 0.5% cobalt excellent excellent gelled acetate and7% glycerin 4E2 4E with 7% glycerin good/ good/ gelled excellentexcellent 4E3 4E with 3.5% sorbitol good/ fair/good gelled excellent 4E44E with 8% glycerin excellent excellent gelled 4FMaltodextrin/propylated/ good/ good gelled unmodified starch + excellentglycerin 4F1 4F with 8% glycerin good/ good gelled excellent 4F2 4F with10% glycerin good/ good gelled excellent 4F3 4F with 12% glycerin good/good gelled excellent 4F4 4F with 15% glycerin good/ excellent gelledexcellent

In Example 4E1, cobalt acetate was employed as a drier.

Example 5 and Comparative Example 11 Maltodextrin/PropylatedStarch/Unmodified Starch Blends Made with Jet Cooking and Biocides

Maltodextrin/unmodified starch/propylated starch blends with biocideswere prepared as follows.

maltodextrin propylated unmodified pH after slurry starch slurry starchslurry water glycerin mixing Final Sample g (%) g (%) g (%) g (%) %ingredients pH 5A 12587.5 1300 984.375 10128   16 3.1 4.0 (37.3) (3.8)(2.9) (40) 5B 11660   1250 937.5  11152.5 16 3.2 4.0 (32.9) (3.5) (2.6)(45) 5C 10335   1200 890.625 12574.3 16.1 3.4 4.0 (28.2) (2.4) (2.4)(50)

Glycerin was added after cooling of sample. The pH was adjusted to theindicated pH level after mixing ingredient together. Final pH wasadjusted as indicated using concentrated H₂SO₄.

All ingredients were mixed together and jet cooked at 310° F. through a5 minute loop.

Bonding strength was tested as described in Example 1 and was asfollows.

Sample Description Paper/Paper PE/Paper 5A Maltodextrin/propylated/ nottested not tested unmodified starch 5B Maltodextrin/propylated/excellent excellent unmodified starch 5B1 Maltodextrin/propylated/excellent good/ unmodified starch - pH excellent 3.15 5CMaltodextrin/propylated/ excellent excellent unmodified starch C11Maltodextrin/propylated/ excellent fair/poor unmodified starch - pH 3.35A2 52.5% excellent good/ Maltodextrin/propylated excellent unmodifiedstarch pH 2.95

Some of the foregoing systems were evaluated for tack property. In thisevaluation, the bonding strength test set forth above in comparativeExample 1 was employed, except that samples were pulled apart after theindicated time and the amount of tack was evaluated.

SAMPLE TIME (Minutes) RESULT PVA 2 Slight Tack 5 Tack 10 50% Wet FiberTear 20 100% Fiber Tear Latex (Dow 2 Tack RAP717NA) 5 10% Fiber Tear,Wet 10 30% Fiber Tear, Wet 20 75% Fiber Tear P30L 2 Very Slight Tack 5Tack 10 Wet Fiber Tear <10% 20 50% Wet Fiber Tear 4A (No Glycerin) 2Nothing 5 Slight Tack 10 Tack, 5% Fiber Tear, Wet 20 Strong Tack 4A 2Nothing 5 Very Slight Tack 10 Slight Tack 20 Tack 4A + .1% 2 NothingManganese Acetate 5 Very Slight Tack 10 Slight Tack 20 Tack 4A + .3% 2Nothing Manganese Acetate 5 Slight Tack 10 Tack 20 Strong Tack 4A + .5%2 Nothing Manganese Acetate 5 Slight Tack 10 Tack 20 Strong Tack 4A + 3%2 Nothing Manganese Acetate 5 Slight Tack 10 Tack 20 Strong Tack 4A + 3%2 Nothing BACOTE 5 Very Slight Tack 10 Slight Tack 4A + .25% 2 NothingTRITON 5 Slight Tack 10 Tack 20 Strong Tack

Manganese acetate is a drier. BACOTE is a cross-linking agent thatincludes ammonium zirconium carbonate. TRITON is a nonionic surfactant.

It is seen that an adhesive that has good polyethylene-to-paper bindingmay be prepared. The adhesive may be made to have a good tack property.In many embodiments, the adhesive is suitable as a lamination adhesive.The adhesive may be used in other applications; for instance, it iscontemplated that the adhesive may be used as a seam adhesive.

Uses of singular terms such as “a,” “an,” are intended to cover both thesingular and the plural, unless otherwise indicated herein or clearlycontradicted by context. The terms “comprising,” “having,” “including,”and “containing” are to be construed as open-ended terms. Allreferences, including publications, patent applications, and patents,cited herein are hereby incorporated by reference. Any description ofcertain embodiments as “preferred” embodiments, and other recitation ofembodiments, features, or ranges as being preferred, or suggestion thatsuch are preferred, is not deemed to be limiting. The invention isdeemed to encompass embodiments that are presently deemed to be lesspreferred and that may be described herein as such. All methodsdescribed herein can be performed in any suitable order unless otherwiseindicated herein or otherwise clearly contradicted by context. The useof any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended to illuminate the invention and does notpose a limitation on the scope of the invention. Any statement herein asto the nature or benefits of the invention or of the preferredembodiments is not intended to be limiting. This invention includes allmodifications and equivalents of the subject matter recited herein aspermitted by applicable law. Moreover, any combination of theabove-described elements in all possible variations thereof isencompassed by the invention unless otherwise indicated herein orotherwise clearly contradicted by context. The description herein of anyreference or patent, even if identified as “prior,” is not intended toconstitute a concession that such reference or patent is available asprior art against the present invention. No unclaimed language should bedeemed to limit the invention in scope. Any statements or suggestionsherein that certain features constitute a component of the claimedinvention are not intended to be limiting unless reflected in theappended claims. Neither the marking of the patent number on any productnor the identification of the patent number in connection with anyservice should be deemed a representation that all embodiments describedherein are incorporated into such product or service.

1-20. (canceled)
 21. An adhesive consisting essentially of: anunmodified or slightly thinned starch; a partially hydrolyzed starchderivative, the starch derivative being present in an amount effectiveto provide affinity to polyethylene; and a modified starch present in anamount effective to inhibit retrogradation of the adhesive.
 22. Theadhesive of claim 1, wherein the partially hydrolyzed starch derivativeis maltodextrin.
 23. The adhesive of claim 1 having a solids contentgreater than 30%.
 24. The adhesive of claim 1 having a solids contentgreater than 50%.
 25. The adhesive of claim 1, the partially hydrolyzedstarch derivative comprising a maltodextrin.
 26. The adhesive of claim1, the modified starch comprising a propylated starch.
 27. The adhesiveof claim 1, wherein the unmodified or slightly thinned starch is presentin a range of about 1-15 wt. %; the partially hydrolyzed starchderivative is present in a range of about 25-75 wt. %; and the modifiedstarch is present in a range of from about 1-15 wt. %.
 28. An adhesiveconsisting essentially of: an unmodified or slightly thinned starch; apartially hydrolyzed starch derivative, the starch derivative beingpresent in an amount effective to provide affinity to polyethylene; amodified starch present in an amount effective to inhibit retrogradationof the adhesive; and a plasticizer.
 29. The adhesive of claim 8, whereinthe partially hydrolyzed starch derivative is maltodextrin.
 30. Theadhesive of claim 8 having a solids content greater than 30%.
 31. Theadhesive of claim 8 having a solids content greater than 50%.
 32. Theadhesive of claim 8, wherein the plasticizer is glycerin.
 33. Theadhesive of claim 8, the partially hydrolyzed starch derivativecomprising a maltodextrin.
 34. The adhesive of claim 8, the modifiedstarch comprising a propylated starch.
 35. The adhesive of claim 8,wherein the unmodified or slightly thinned starch is present in a rangeof about 1-15 wt. %; the partially hydrolyzed starch derivative ispresent in a range of about 25-75 wt. %; and the modified starch ispresent in a range of from about 1-15 wt. %.
 36. The adhesive of claim15, wherein the plasticizer is present in a range of from 1-30 wt. %.37. The adhesive of claim 16, wherein the plasticizer is glycerin.